*Enrico Gilrandy Wahyu Suharjo¹、Ryohei Takahashi¹、Andrea Agangi¹、Pearlyn Manalo¹、Hinako Sato¹、Syafrizal Syafrizal²、Mochamad Slamet Sugiharto³、Anton Murtono³ (1.Graduate School of International Resource Sciences, Akita University, Japan、2.Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology, Indonesia、3.Exploration Division, PT Timah, Indonesia)